Incineration provides acceptable means for disposing of waste, oxidation of materials, and for recovery of heat from burning refuse; however, the process of incineration has had imposed on its use severe and substantial limitation. Some incinerators require removal of materials not fully combustable in prior systems or burnable only with undesirable side effects or hazards; thus a sorting step is necessary for use of such processes and equipment. Other incinerators need shredded material for burning and that prerequisite also requires extra processing and equipment. Most prior art incinerators are incapable of meeting environmental standards, and require one or more of a wide range of auxiliary equipment, such as afterburners, scrubbers, precipitators and the like to make them function properly.
Even with suitable pre-incineration processes and equipment and auxiliary environmental protection devices, full combustion of random refuse material is seldom achieved, because adequate oxygenation of the burning particles is required, although the burning cannot be so rapid as to make the fire to hot or permit excessive gasification or atomization of the burning particles or the products of combustion. Optimum non-polluting combustion requires close control of the time, turbulence and temperature of the burning process. The problem is further magnified when the refuse contains plastics, wet refuse and liquids and when unburned particles are permitted to escape from the main burning chamber.
The main burning chamber of an incinerator has a hearth floor. The use of a hearth has some inherent problems requiring solution for effective and efficient combustion of random refuse. The refuse on the hearth must receive an even distribution of oxygen for the material to burn. Air must be mixed with the burning material and dispersed. Air alone, particularly with high velocities, will entrain and lift burning particles before they are fully consumed. The uncontrolled rapid burning of the pile may also increase velocities. Such high velocities and the accompanying incomplete burning results in slagging and tends to clog up the incinerator floor, as well as to permit incompletely burned particulates and products of combustion to exit the main burning chamber of the incinerator before they are adequately consumed.
A variety of United States patents have addressed the problems of incinerator hearths. A variety of configurations have been described for the solving of various problems.
U.S. Pat. No. 4,706,578, issued on Nov. 17, 1987, describes a pulsating incinerator hearth in which the hearth is suspended on a fixed frame for movement in a limited short arc so as to urge random sized particles to move along a predetermined path along the surface of the hearth. The movement is imparted to the hearth in periodic pulses by inflating airbags mounted on the frame. These airbags stroke the hearth so as to move it a short distance from an initial position and to jar it against the frame. This causes the burning particles to move a short distance by inertia. In addition, this hearth also includes a plurality of nozzles that are connected to a source of air for delivering gently flowing air to the burning pile on the hearth.
U.S. Pat. No. 4,491,077, issued on Jan. 1, 1985, also discusses a vibrating hearth burner. This vibrating hearth provides uniformity of fuel combustion by providing a burner in which the grate and the vibrating mechanism cooperate to decelerate the movement of fuel across the grate as it travels toward the discharge end. This device utilizes an ash return shute which is incorporated into the vibrating grate assembly. The vibrating assembly keeps the ash in motion as it returns to the rear end adjacent the delivery end of the grate. There is an air flow through the fuel material on the grate.
U.S. Pat. No. 4,771,710, issued on Sep. 20, 1988, shows a stepwise grid for waste incineration furnaces having improved air circulation and air tightness. Specifically, this device includes side joint coverings that protrude from one side of the grid. The side joint coverings secure the tightness against the infiltration of waste between the adjacent steps of the process. This invention shows a moving hearth in combination with such covered joints.
Various other moving hearth furnaces are disclosed in U.S. Pat. Nos. 4,702,178, 4,667,609, and 4,241,671. In these moving hearth type furnaces, air is circulated for the purpose of increasing the burn on the hearth. U.S. Pat. Nos. 3,958,920 and 4,046,085 describe moving hearth furnaces where the air is controlled for a complete burn of waste products.
Importantly, none of the prior art devices have recognized the need for the cooling of the metal hearth during the burn process. As such, although the moving hearths attempt to cause the burned particles to move, they do not accommodate the problem of slag accumulation. Also, these are not effective for the containment of the ash particles within the primary combustion chamber. During the combustion process, the ashen materials are generally left free to disperse throughout the hearth region. As a result, significant clogging or damage is caused by the uncontrolled distribution of ash particles.
The above-stated problems are particularly important in the disposal of medical wastes. Medical wastes are often hazardous. As such, it is particularly important to have a complete burn of the materials introduced into the incinerator. It is dangerous and destructive to leave certain hazardous medical wastes unburned. As such, it is important to contain the materials on the hearth during the burning process. Also, much of the medical waste is liquid. Whenever a liquid is introduced to a hearth, it tends to disperse quickly and to flow everywhere. As such, it is important to design a hearth that effectively contains any liquid medical waste on the hearth until the burning of such waste is completed.
It is an object of the present invention to provide a hearth that effectively contains the materials until a complete burn is achieved.
It is another object of the present invention to provide an improved hearth that effectively contains and destroys liquid waste.
It is another object of the present invention to provide a hearth that prevents slag accumulation.
It is still object of the present invention to provide an oscillation hearth within a combustion chamber which allows the burned particles to pass in a systematic manner to a receptacle.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.